Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Ch 4: Types of Rxns and Solution...

Copyright©2000 by Houghton Mifflin Company. All rights reserved.

1

Ch 4: Types of Rxns and Solution Stoik

• Read for comprehension pp 131 - 147


2

Aqueous Solutions

Water is the dissolving medium, or solvent.


3

Some Properties of Water

Water is “bent” or V-shaped. The O-H bonds are covalent. Water is a polar molecule. Hydration occurs when salts dissolve in

water.


4

Figure 4.1 The Water Molecule is Polar


5

Solute/Solvent

Solute: -- dissolves in water (or other “solvent”) --is present in lesser amount (if the same phase as

the solvent)Solvent: --is present in greater amount (if the same phase as

the solute)


6

Like Dissolves Like

• Rule of thumb: polar solvents dissolve

polar/ionic solutes

nonpolar solvents dissolve

nonpolar solutes


7

Figure 4.2Polar Water Molecules Interact with the Positive and Negative Ions of a

Salt


8

Figure 4.3Polar Bond in ethanol


9

Figure 4.5BaCl2 Dissolving

Dissociation:

BaCl2(s) --> Ba2+(aq) + 2Cl-(aq)


10

Electrolytes

Strong - conduct current efficiently Salts: NaCl

Strong acids: HNO3

Strong bases

Weak - conduct only a small current Weak acids/bases:acetic

acid/ammoniaTap water

Non - no current flowspure water, sugar solution


11

Acids

Strong acids - dissociate completely to produce H+ in solution

hydrochloric and sulfuric acid

Weak acids - dissociate to a slight extent to give H+ in solution

acetic and formic acid


12

Figure 4.6HCI (aq) is Completely Ionized


13

Figure 4.8Acetic Acid in Water


14

Bases

Strong bases - react completely with water to give OH ions.

sodium hydroxide

Weak bases - react only slightly with water to give OH ions.

ammonia


15

Figure 4.7An Aqueous Solution of Sodium Hydroxide


16

Figure 4.9The Reaction of NH3 in Water


17

Molarity

Molarity (M) = moles of solute per volume of solution in liters:

M

M

= =

=

molaritymoles of soluteliters of solution

HClmoles of HCl

liters of solution3

62


18

Common Terms of Solution Concentration

Stock - routinely used solutions prepared in concentrated form.

Concentrated - relatively large ratio of solute to solvent. (5.0 M NaCl)

Dilute - relatively small ratio of solute to solvent. (0.01 M NaCl)


19

Figure 4.10Preparation of a Standard

Solution


20

Figure 4.11(a) A Measuring Pipet (b) A

Volumetric (transfer) Pipet


21

Types of Solution Reactions

Precipitation reactionsAgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)

Acid-base reactionsNaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)

Oxidation-reduction reactionsFe2O3(s) + Al(s) Fe(l) + Al2O3(s)


22

Simple Rules for Solubility

1. Most nitrate (NO3) salts are soluble.

2. Most alkali (group 1A) salts and NH4+ are soluble.

3. Most Cl, Br, and I salts are soluble (NOT Ag+, Pb2+, Hg22+)

4. Most sulfate salts are soluble (NOT BaSO4, PbSO4, HgSO4, CaSO4)

5. Most OH salts are only slightly soluble (NaOH, KOH are soluble, Ba(OH)2, Ca(OH)2 are marginally soluble)

6. Most S2, CO32, CrO4

2, PO43 salts are only slightly soluble.


23

Figure 4.14The Reaction of K2CrO4(aq) and

Ba(NO3)2(aq)


24

Describing Reactions in Solution

1. Molecular equation (reactants and products as compounds)

AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)

2. Complete ionic equation (all strong electrolytes shown as ions)

Ag+(aq) + NO3(aq) + Na+(aq) + Cl(aq)

AgCl(s) + Na+(aq) + NO3(aq)


25

Describing Reactions in Solution (continued)

3. Net ionic equation (show only components that actually react)

Ag+(aq) + Cl(aq) AgCl(s)

Na+ and NO3 are spectator ions.


26

Figure 4.16The Reaction of KCI(aq) and AgNO3(aq)


27

Performing Calculations for Acid-Base Reactions

1. List initial species and predict reaction.

2. Write balanced net ionic reaction.

3. Calculate moles of reactants.

4. Determine limiting reactant.

5. Calculate moles of required reactant/product.

6. Convert to grams or volume, as required.


28

Key Titration Terms

Titrant - solution of known concentration used in titration

Analyte - substance being analyzed

Equivalence point - enough titrant added to react exactly with the analyte

Endpoint - the indicator changes color so you can tell the equivalence point has been reached.


29

Rules for Assigning Oxidation States

1. Oxidation state of an atom in an element = 0

2. Oxidation state of monatomic element = charge

3. Oxygen = 2 in covalent compounds (except in peroxides where it = 1)

4. H = +1 in covalent compounds

5. Fluorine = 1 in compounds

6. Sum of oxidation states = 0 in compounds Sum of oxidation states = charge of the ion


30

Balancing by Half-Reaction Method

1. Write separate reduction, oxidation reactions.

2. For each half-reaction:

Balance elements (except H, O)

Balance O using H2O

Balance H using H+

Balance charge using electrons


31

Balancing by Half-Reaction Method (continued)

3. If necessary, multiply by integer to equalize electron count.

4. Add half-reactions.

5. Check that elements and charges are balanced.


32

Half-Reaction Method - Balancing in Base

1. Balance as in acid.

2. Add OH that equals H+ ions (both sides!)

3. Form water by combining H+, OH.

4. Check elements and charges for balance.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Ch 4: Types of Rxns and Solution...

Documents

Transcript of Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Ch 4: Types of Rxns and Solution...